Photogrammetrische Messmethoden

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Automatisierte Medienanalyse

Erkannte Entitäten
The Federal Waterways Engineering and Research Institute in Karlsruhe, the BAW, conducts research in its laboratories using large physical models. Optical measuring methods are applied to yield high quality and high quantity data. Great precision is essential. In the model of the Obernau weir near Aschaffenburg the flow behaviour of the River Main is being examined at various water levels. A machine specially designed in
the BAW dispenses white polypropylene discs at programmable frequency and
controllable quantities. These tracers, as
they're called, precisely follow the flow on the water surface. They're carried along by the current and make it clearly visible.
A fixed camera records their course. From the data gathered a computer then evaluates the flow behaviour. The technique is known as 2-dimensional particle-tracking velocimetry - PTV for short - which records surface speed on camera. The 4 light points marked are the precisely calculated reference points. For a 1-camera measuring system all the points must be at the same level, floating on the surface of the water.
This solid-bed half model of the River Elbe near Schönberg is to measure currents in the the groyne fields. Reference points again provide orientation and correlation. All the points are different. They each have their own
circular barcode. For the 3-camera
system used here, the points don't have to be in the same measuring plane. The tracers make the flow behaviour in a groyne field visible - shown here in time-lapse. The groynes here have cut-out sections, which are designed to change flow behaviour.
The tracers are filmed by 3 cameras and can therefore be evaluated three-dimensionally. The water level, the
position of the tracers and their speed in the flow can be ascertained at one and the same time. The computer evaluation can then depict the flow behaviour in the groyne field. Here we see the velocities and here the water levels.
This measuring gantry above a model of the River Oder can be manoeuvred to any point in the model. Before it's used on
the model, the 3-dimensional measuring system has to be spatially calibrated. The reference points are fixed at different heights for this.
The configuration of the three cameras to one another on the rigid frame is measured.
This has to remain constant during the whole measuring procedure.
Here too, the features and orientation of all the components in the system, such as sensors and lenses, must be precisely determined before every measurement. With the calibration completed, measuring can begin. The three
cameras take pictures of the surface from different angles.
The reference points enable the measured data to be collated.
From above, a grid pattern is projected down onto the surface of the model. The spatial
position of every point on the grid can now be ascertained via triangulation. An expanded version of this system also ascertains the mean water level in the measuring field at the same time. The optical
paths of the video cameras
are calculated. Then the underwater changes on the river bed can also be measured during the test. This 3-dimensional terrain model consists of a total of 4,000 individual data sets, taken every 10 seconds over a period of 11 hours. The different colours show the different levels of the river bed. Red represents higher areas, green deeper levels. Using numerical models, computed on the basis of the data gained from
the physical model, the course of a ship travelling upstream can be simulated. The ship seeks the best course for avoiding shallows. A number of variants are examined. The dynamic simulation process - also developed by the BAW - takes account of the physical characteristics of the ship.
Optisches Bauelement
Kaliber <Walzwerk>


Formale Metadaten

Titel Photogrammetrische Messmethoden
Alternativer Titel Photogrammetric Measuring Methods
Autor Schledding, Thomas
Mitwirkende Bernd Hentschel (wissenschaftliche Betreuung)
Thorsten Hüsener (wissenschaftliche Betreuung)
Kuno Lechner (Kamera)
Uwe Fanelli (Kamera)
Thomas Gerstenberg (Ton)
Andreas Grimm (Ton)
Abbas Yousefpour (Schnitt)
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DOI 10.5446/14869
IWF-Signatur C 13225
Herausgeber Bundesanstalt für Wasserbau (BAW)
Erscheinungsjahr 2010
Sprache Englisch
Produzent IWF
Produktionsjahr 2008

Technische Metadaten

IWF-Filmdaten Video-Clip ; F, 5 min

Inhaltliche Metadaten

Fachgebiet Technik
Abstract Optische Messverfahren in den physikalischen Modellen der BAW bringen qualitativ und quantitativ hochwertige Daten. Mit dem 2-D-Partikel-Trecking-Velocimetrie Verfahren wird die Oberflächengeschwindigkeit mit einer Kamera erfasst. 3 Kameras erfassen bei 3-D-Partikel-Tracking-Velocimetrie die Wasserspiegellagen und die Oberflächengeschwindigkeit im Modell dreidimensional. Drei Kameras nehmen auch photogrammetrisch durch das Wasser hindurch die Geometrie und Veränderung der Flusssohle während des Versuchs auf. Die Daten fließen in numerische Modelle ein, mit denen auch weitergehende fahrdynamische Analysen durchgeführt werden..
Optical measuring methods applied the physical models of the BAW yield high quality and high quantity data. Using 2D particle tracking velocimetry, one camera records the velocity of the water surface. Using the 3D particle tracking velocimetry, three cameras are recording in three dimensions the water level and the surface velocity in the model at the same time. Three cameras also measure photogrammetrically the geometry and the changes of the river bed through the water during the ongoing experiment. Data are used in numerical models with which further dynamic analysis is performed.
Schlagwörter Modell, fahrdynamisches
Modell, physikalisches
hydraulic engineering
particle tracking velocimetry
1 camera system
3 cameras system
flow rating
water surface velocity
groyne field
physical model
numerical model
dynamic of ship movement

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